This project is based on the hypothesis that neural mechanisms in the control of respiration are more important than traditionally believed. The studies have involved the development of methods to quantify the neural discharge of a respiratory nerve, the phrenic, in terms of respiratory drive, and are being extended to include another respiratory motor nerve, the recurrent laryngeal. Using these indicators in animals with the chemical feedback loop opened, the input-output characteristics of the respiratory control system to neural stimuli are being studied. Specifically, the ability of the control system to maintain its output as the result of self-stimulation or self-amplification at a medullary-pontine level is being studied. The current approach is to demonstrate this mechanism in an isolated brainstem preparation, i.e., with supracollicular decerebration and separation of the spinal cord from the medulla. Input will be made via the carotid sinus nerve and output from a branch of the vagus nerve, the recurrent laryngeal. It is hoped to show that feedback or self-stimulating process is localized in the medulla and pons. BIBLIOGRAPHIC REFERENCES: Eldridge, F.L. Central Neural Stimulation of Respiration in Unanesthetized Decerebrate Cats. J. Appl. Physiol. 40:23-28, 1976. Eldridge, F.L., and K.Z. Vaughn. Effect of Changing Lung Volume on Occlusion Pressures: Muscular Effects. Federation Proc. 35:633, 1976.